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Speed Review: Road environment, behaviour, speed limits, enforcement and crashes


Federal Office of Road Safety - Contract Report 127

Full report in .pdf format [7.5MB]


A study was undertaken to review the role of vehicle speed in road crashes, speed limits, enforcement and behaviour, and the environment. A review of the international literature was initially carried out to highlight overseas findings and issues identified for further research and development. Visits were also made to a select number of overseas research and government agencies in Scandinavia, Europe and the United States to gain first hand knowledge of problems and research being undertaken in these countries. A meeting was then organised of 45 Australian experts with research, government authority, and motoring backgrounds, as well as a keynote speaker from Sweden, to identify current problems and issues in Australia. From this extensive review, 22 items requiring further research and 12 action items were identified and prioritised in terms of their importance and value for reducing speed related crashes. Prominent topics requiring future research were the development and exploitation of perceptual countermeasures, the credibility of speed zone limits, road design and travel speed, speed and crash involvement and behavioural correlates, the effectiveness of Local Area Traffic Management (LATM) devices, enforcement tolerance and travel speed, safety consequences of changes to speed limits, and more travel speed and crash speed data. Priority items for future action programs included greater use of low cost perceptual road treatments, a trial program of top speed limiters for cars, need for a change in community attitude towards speeding, an Australia-wide expert system for determining speed limits, speed zone policy and practice publicity, more repeater signing in speed zones, and widespread use of effective speed reduction technologies.

Executive Summary

Speeding has long been recognised as a major factor in many road crashes. Excessive speed was noted as a definite cause in 8 percent of crashes and up to twice that as a probable cause in studies overseas. In Australia, excessive speeding has been noted as a contributing factor in up to 30 percent of fatal crashes. On these statistics, speed related road trauma is likely to cost the Australian community up to A$1 billion annually.

Much is already known about the consequences of excessive speed in a crash. The faster the impact speed, the greater the likelihood of severe injury or death in a collision as predicted by physics. This relationship is further evident by reports on the consequences of changes in speed limits where the overwhelming weight of evidence shows that if actual travel speeds are reduced, there will be a resultant decrease in the number of injuries and severe trauma on the road.

Less is known, however, about how excessive speed leads to crashes. Early reports suggested that large variances above or below the mean traffic speed were associated with increased risk of crash involvement. However, much of this evidence is old and somewhat biased and therefore not particularly conclusive. This is primarily because accurate and comprehensive information on travel speed at the time of collision has not been readily available.

Furthermore, knowledge of the effects of speed limits, speed enforcement, and the environment on influencing travel speed and therefore crashes is fragmented and lacks clear direction for use in speed management intervention.

With this in mind, the Road Safety Bureau of the Roads and Traffic Authority (NSW) along with the Federal Office of Road Safety recently commissioned the Monash University Accident Research Centre to undertake a detailed review of the role of speed in a number of important areas to highlight directions for future research and action aimed at reducing speed related trauma.


The project specification called for a review of four specific speed related topics, namely the relationship between speed and crashes, the role of speed limits on travel speed, the effects of speed enforcement on travel speed and driver behaviour, and the influence of the environment on speeding. A number of separate tasks were undertaken during the course of this review.

Literature Review

First, a thorough review of the international literature was undertaken to highlight what had been previously reported in the four key speed areas of crashes, speed limits, enforcement and behaviour, and the environment. Over 250 references were located and critically reviewed to outline previous findings and shortcomings from this body of research knowledge. From this extensive review, a number of conclusions and options for future research and development were able to be outlined.

Overseas Visits

Visits were made to a number of key research and government agencies in Scandinavia, Europe, and the United States to discuss current speeding issues and interventions, either operating or planned for the future in these regions. Attention was also given to past efforts in this area and what lessons were to be learned from these experiences.

Senior officers of MUARC undertook these visits during recent overseas trips and provided extensive reports on the outcomes of their visits to the study team. These are found, along with other specialist papers, in the Appendices at the back of this report.

Speed Workshop

A one-day workshop was then arranged in conjunction with the Road Safety Researcher's Conference in Canberra to consider the findings from the review and the overseas visits and especially how they translate to current Australian speed management issues. Forty-five Australian experts in road safety with a specific interest in speed were invited to attend this meeting.

In addition, Dr. Göran Nilsson of the Swedish Road and Traffic Research Institute was brought to Australia as a keynote speaker for the workshop. Dr. Nilsson has had an extensive background in speed research and management in Sweden and the rest of Europe and was able to provide an excellent overview of current problems and initiatives in a number of these countries.

As well as invited presentations, the workshop included four "brain-storming" sessions, each one addressing one of the four key speed related topics outlined by the project objectives. The findings from each of the workshops have been documented in this report.

Prioritising Future Research and Action

From the wealth of information gathered during the course of this project, 22 research and 12 action items were identified requiring further attention for speed management intervention in this country.

These items were listed along with indications of how they could be undertaken, what would be the expected outcome, how easy or difficult they would be to carry out, and the likely cost of the research or the action. Lists were then distributed to each workshop participant who was asked to rank these items in terms of their importance and value. These rankings were then summed across all respondents to provide a consensus view on speed priorities.


A number of important research topics were identified and prioritised for future efforts aimed at improving knowledge and/or reducing the number and severity of speed related crashes in Australia. The eight most pressing topics included:

  • the identification (and exploitation) of perceptual countermeasures against speeding,
  • speed zoning and the credibility of these speed limits among motorists,
  • the relationship between road design and travel speed,
  • understanding the relationship between crash involvement and travel speed and the behavioural explanations for speeding,
  • the effectiveness of Local Area Traffic Management devices in reducing travel speed and crashes,
  • the consequences of enforcement tolerances above the speed limit on travel speed behaviour,
  • confirmation of overseas findings regarding the safety consequences of changes in the posted speed limit, and
  • the collection of more accurate and extensive speed and crash data.


As well as the research items, a number of action programs were identified that could be undertaken immediately to reduce speed related trauma in this country. The most prominent of these were:

  • greater use of low cost road treatments to modify driver's perceptions of the road and environment to reduce travel speed,
  • introduction of top speed limiters on a suitable sample of passenger cars to demonstrate their likely effectiveness,
  • the development of public education programs to promote a widespread change in community attitudes to speeding, similar to that experienced with drink-driving,
  • the development of an Australia-wide system for determining appropriate speed limits based on existing expert systems,
  • education and publicity among motorists of current speed zone policies and practices throughout Australia,
  • greater attention to repeater signing of speed limits within zones to ensure motorists are aware of these speed limits, and
  • the more wide-spread use of available and effective speed enforcement technologies in all States and Territories.